CVE-2014-4975 in Ruby
Summary
by MITRE
Off-by-one error in the encodes function in pack.c in Ruby 1.9.3 and earlier, and 2.x through 2.1.2, when using certain format string specifiers, allows context-dependent attackers to cause a denial of service (segmentation fault) via vectors that trigger a stack-based buffer overflow.
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Analysis
by VulDB Data Team • 05/10/2026
The vulnerability identified as CVE-2014-4975 represents a critical off-by-one error within the Ruby programming language's internal pack.c file, affecting versions 1.9.3 and earlier, as well as Ruby 2.x through 2.1.2. This flaw resides in the encodes function which processes format string specifiers during data encoding operations. The vulnerability manifests when specific format string combinations are utilized, creating a scenario where memory boundaries are improperly handled. The underlying issue stems from inadequate bounds checking during stack buffer operations, allowing malicious input to overwrite adjacent memory locations. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient validation permits data to be written beyond the allocated buffer boundaries. The flaw is context-dependent, meaning its exploitation requires specific conditions to be met, typically involving crafted input that triggers the vulnerable code path during encoding operations. The vulnerability's impact extends beyond simple memory corruption as it can lead to segmentation faults that crash the entire Ruby application or process. When exploited successfully, this vulnerability enables attackers to perform denial of service attacks by causing the targeted Ruby application to terminate unexpectedly. The attack vector specifically involves manipulating format string specifiers in encoding functions, which are commonly used in data processing, network communication, and file handling operations within Ruby applications. This vulnerability directly impacts the integrity and availability of Ruby-based systems, as attackers can force applications to crash repeatedly through carefully crafted inputs. The exploitation requires minimal privileges since it operates within the context of the Ruby interpreter itself, making it particularly dangerous in web applications where user input is frequently processed through encoding functions.
The technical implementation of this vulnerability demonstrates how a seemingly minor programming error can result in significant security implications. The off-by-one error occurs during the calculation of buffer sizes needed for specific format string operations, where the boundary checks fail to account for the exact memory requirements. When Ruby processes format strings containing certain combinations of specifiers, the encodes function attempts to allocate stack space for the resulting encoded data. However, due to the miscalculation in buffer size determination, the allocated space is insufficient for the actual data being written. This discrepancy causes the program to write beyond the allocated stack buffer, potentially overwriting critical memory segments including return addresses, local variables, and other program state information. The vulnerability is particularly insidious because it can be triggered through normal application usage patterns without requiring specialized tools or conditions. The stack-based buffer overflow occurs during runtime when the vulnerable function executes, making it difficult to detect through static analysis alone. The segmentation fault that results from this overflow typically manifests as an application crash, though in some cases it could potentially be leveraged for more advanced exploitation techniques if additional vulnerabilities exist in the system. The flaw's exploitation is not limited to simple denial of service but represents a fundamental breakdown in memory safety mechanisms within the Ruby interpreter's core functionality.
The operational impact of CVE-2014-4975 extends across numerous Ruby-based applications and systems that rely on encoding operations for data processing. Web applications using Ruby frameworks such as Ruby on Rails are particularly vulnerable since these frameworks frequently employ encoding functions for handling user input, processing HTTP requests, and managing data transfers. The vulnerability affects not only standalone Ruby applications but also complex systems where Ruby serves as an embedded scripting language or integration component. Organizations running Ruby-based services, including e-commerce platforms, content management systems, and web applications, face significant risk from this vulnerability. The denial of service aspect makes it particularly attractive to attackers seeking to disrupt service availability, potentially leading to revenue loss and reputational damage. The vulnerability's presence in multiple Ruby versions means that a wide range of systems could be affected, from legacy applications still using Ruby 1.9.3 to newer applications utilizing Ruby 2.1.2. In enterprise environments, this vulnerability could impact critical business applications, automated processing systems, and integration platforms that depend on Ruby's data handling capabilities. The attack surface is broad since encoding operations are fundamental to data processing, making it likely that any Ruby application processing external input could be vulnerable. The vulnerability also impacts systems where Ruby is used for system administration tasks, network automation, and scripting operations, where the potential for exploitation through crafted input is significant.
Mitigation strategies for CVE-2014-4975 primarily focus on upgrading to patched versions of Ruby where the vulnerability has been resolved through proper bounds checking and buffer size calculations. The most effective approach involves immediate patching of affected Ruby installations to versions that contain the necessary fixes. Organizations should implement comprehensive vulnerability management processes to identify all systems running affected Ruby versions and prioritize their remediation. Additionally, input validation and sanitization practices should be strengthened to reduce the likelihood of exploitation through crafted format strings. Implementing proper error handling and defensive programming techniques can help detect and prevent malformed input from reaching vulnerable functions. Security monitoring should be enhanced to detect unusual patterns of application crashes or segmentation faults that might indicate exploitation attempts. Network segmentation and access controls can limit the potential impact of successful exploitation by restricting access to vulnerable applications. Regular security assessments and penetration testing should include verification that Ruby applications are not vulnerable to this type of buffer overflow. The vulnerability also underscores the importance of maintaining updated security patches across all system components, as Ruby's encoding functions are commonly used throughout various application layers. Organizations should consider implementing runtime protection mechanisms or application firewalls that can detect and block malicious input patterns targeting this specific vulnerability. The fix for this vulnerability typically involves correcting the buffer size calculation logic in the encodes function to properly account for all possible output requirements, ensuring that the allocated stack space is sufficient for the data being processed.